Imagine going to the polls on election day and your polling location has been shut down or your right to vote challenged or worse, you're taunted by people at the polling site because you're a person of color.

These are just some of the concerns that civil rights groups around the country have as early voting begins. Groups representing Latino, Black, Asian, Arab and Muslim-American voters are preparing for what they expect will be a confusing and contentious presidential election.

"We are on the precipice of the most chaotic election for people of color in 50 years," said Wade Henderson, president of the Leadership Conference on Civil and Human Rights on Wednesday. "We are doing everything we can to prevent discrimination, intimidation and violence at the polls."

Henderson and other civil rights groups say they are growing particularly worried as Donald Trump ratchets up claims that the election is "rigged" and calls for his supporters to monitor the polls.

On Wednesday, a group named the Oath Keepers called on "retired police officers, our military intelligence veterans, and our Special Warfare veterans" to "apply their considerable training in investigation, intelligence gathering, and field-craft to help stop voter fraud."

In response to the Oath Keepers' release, Kristen Clarke, president and executive director of the Lawyers' Committee for Civil Rights Under Law, issued a statement: "There is no place in our democracy for this form of vigilantism and extremism," particularly since "their efforts seem directed against minority communities." The organization is urging voters to call 866-OUR-VOTE if they encounter intimidation tactics at the polls.

Rev. Dr. William Barber, the president of the North Carolina NAACP, said his offices have been "inundated with complaints" since early voting began in the state. In a conference call Thursday, Barber noted reports of hecklers photographing black voters during events and one instance where KKK-inspired graffiti was written on a street in front of a black church where a "souls to the polls" event was being held.

"It is, in fact, voter suppression that is the legal threat in this election," Barber said.

The NAACP noted that more than 100 voters in Beaufort County, North Carolina, had their voter registration challenged after local residents raised questions to the local election bureau about whether they could legally vote in the county. Of that group, nearly 60% of the residents whose voting rights were being challenged were African-American, the NAACP said.